Electric power steering apparatus which assist a steering force of a vehicle using a driving force of a motor has been known. Among such electric power steering apparatus, a column-type electric power steering apparatus which transmits a driving force of a motor to a steering shaft such as a steering column has been introduced.
Generally, an electric power steering apparatus controls a motor based on driving conditions such as a vehicle speed and a steering torque obtained from a vehicle speed sensor and a steering torque sensor to assist a steering force and to enhance a steering feeling.
In a column-type electric power steering apparatus, a worm gear is provided to a worm shaft which is connected to an outer shaft of a motor and a worm wheel is provided to a steering shaft, and the worm gear and the worm wheel are engaged with one another so that a driving force of a motor is transmitted to a steering shaft.
Such a column-type electric power steering apparatus may be exposed to problems of increase of backlash by clearance due to abrasion of gears or manufacturing clearance and vibration or noise. In order to solve these problems, an electric power steering apparatus having a tilting structure which tilts a worm shaft toward a worm wheel so as to compensate clearance due to abrasions has been introduced.
A conventional tilting structure has a structure extruded to the outside of an electric power steering apparatus, so it may be released or broken by external shock, and since it is configured to be able to regulate a tilting amount, clearance of a tilting structure and assembling clearance may also be added and this may negatively affect the performance of an electric power steering apparatus.